1. Field of the Invention
The present invention relates generally to the field of fabricating of silicon, more particularly, to the methods of manufacturing of silicon in substantially crystalline form out of amorphous silicon.
2. Background Information
Crystalline silicon is an important material widely used in a variety of applications. One way to prepare crystalline silicon is by the process of metal-induced crystallization of amorphous silicon to form large-grained polycrystalline silicon templates. Such silicon crystals can be used for manufacturing of various devices requiring the use of thin films. Examples of such devices include solar cells, thin film transistors, microelectromechanical (MEMs) devices and optical waveguides for various telecommunications applications. To illustrate, in the process of fabrication of solar cells, large-grained polycrystalline silicon templates can be prepared first. Epitaxial thin silicon films can then be grown on the polycrystalline silicon templates, to be used in high-efficiency solar cells and high minority lifetime silicon material, fabricated on inexpensive glass substrates.
One of methods currently used for making the crystalline silicon out of amorphous silicon includes incorporating a reactive metal into amorphous silicon, followed by annealing. The metal particles are intended to nucleate amorphous silicon and to induce the process of crystallization which can lead to the formation of silicon crystals having grain sizes as large as 100 micrometers. However, the currently used processes typically require using high annealing temperatures, or prolonged periods of annealing, or both. Thus, the process requires long times, and thus is expensive, and, due to incompatibility of low-cost substrates with high annealing temperatures, the quality of the final polycrystalline silicon can in some cases be inadequate. Accordingly, it is desirable to have a better process of making the crystalline silicon out of amorphous silicon, such as a faster process requiring lower annealing temperatures.